NLPs are discoidal nanoparticles formed when apolipoproteins and a population of phospholipids self-assemble into nanometer-sized discs containing a bilayer that is fully soluble in an aqueous environment. Nanolipoprotein particles (NLPs) are nanoscale (6-30 nm), discoidal patches of lipid bilayer stabilized by peripheral scaffold. NLPs present distinct advantages over currently used membrane systems in terms of particle size and consistency: the presence of the circular apolipoprotein “belt” that constrains the dimensions of the bilayer and helps ensure discrete NLP particle sizes between preparations compared to current model membranes. The protein belt also makes NLPs more thermally stable over time compared to micelles and liposomes. This bilayer is thought to closely mimic the cell membrane, providing a hydrophobic patch for the incorporation of membrane proteins as well as a region for the interaction of drugs and other small molecules.
Currently, the greatest use of NLPs has been the stabilization and characterization of membrane proteins. Noteworthy, is the fact that these artificial lipid system were more soluble with less sample heterogeneity compared to proteins prepared from microsomes. The combined use of cell-free-NLPs production allows for the soluble presentation of membrane proteins in a highly controlled environment. Cell-free systems also permit unique labeling/tagging strategies not readily available to whole cell systems and allows one to go from a gene to protein to structure in a single day. Cell-free systems can accommodate additives that augment protein expression; including: chaperonins, lipids, redox factors, and detergents and protease inhibitors. More recently GPCRs and model proteins such as bacteriorhodopsin, have been reconstituted into NLPs using DMPC alone, POPC alone or a mixtures of POPC/POPG demonstrating that lipid effects can be used to fine tune NLP applications. Other additives that alter lipid:apoprotein interactions could aid in solubilization and NLPs. Importantly, this can all be accomplished in a single reaction, in a high-throughput manner for testing a variety of conditions to identify optimal functional parameters.
The development of several amphiphilic PEG-dendritic block copolymers (telodendrimers) was previously shown to have several favorable nanoproperties for both cancer imaging and therapy using micelles. The particles were 20-80 nm. This size is generally smaller than many of the reported nanoparticles and liposomes, containing a well-defined and easily fine-tuned PEG corona. Importantly the use of PEG could minimize the nonspecific binding as well as biological degradation in vivo. Although the micelles were designed for packaging drug and imaging agents buried inside the hydrophobic core the telodendrimers themselves provide convenient covalent attachment sites that could be used for presenting active targeting and cellular uptake molecules on the surface. The possibility of incorporating the telodendrimer functionality on a different nanoplatform such as the NLPs could aid in the development of a novel multifaceted nanoparticle capable of carrying therapeutic peptides with imaging functions displayed on the surface of the nanoparticles. Surprisingly, the present invention meets this and other needs.